Fine Motion Mechanisms
Anthony E. Gee, University College, London

Generation and transmission of mechanical motions are generally well-served at ranges of mm with accompanying resolutions in 10s of µm. However, when placement resolution is scaled down to 1µm or less, the activities tend to become applications'-specialized and center on 'local' cultures and techniques. This tutorial examines fundamentals using cross-referencing between examples of design-techniques from alternative sectors.

Sources include optics-manufacture, surface measurement, IT devices (eg optical scanning, disc storage and fiber optics), spectroscopy, instrumental astronomy, microscopy (optical and scanning-probe) and seismometry. Design, function, applications and manufacture of a device, instrument or machine embrace shared principles and commonality with other applications’ areas.

Examples will be viewed from defining specifications and resulting kinematic 6 degree-of-freedom considerations. Insidious effects of friction and wear will be examined and mitigating alternatives offered for motion generation and control applications. Techniques to improve the performance of prismatic planar guide-ways will be considered including load-offset support and alternative 'elastic averaging'.

Rectilinear micro-motion, its reduction and rotary conversion will be considered. Examples of spring-strip levers, electrical and piezoelectric motions, steppers and hydraulic actuators will be examined. Hybrid dual fine-motion and long-range actuators will be considered. 'Parasitic' motions will be considered and a formal approach to multiple degree-of-freedom effects will be shown which optimizes individual axis sensitivities in the intended application/function.

This tutorial offers insights for mechanical designers, instrument engineers and those working at the precision mechanical/electronic interface found within specific applications’ sectors. Underlying philosophy is to maximize precision/cost by design.